Anhydrous sprays for personal care have become popular in recent years because they are easy to apply, go on clear, and require no rubbing to distribute over the skin. Mast personal care sprays use ethanol as a diluent. Ethanol-based continuous sunscreen sprays, although known in some form since the early 1970s (see, e.g., U.S. Pat. No. 3,895,104), are relatively new to the market. Because consumers like using them, such sprays have increased overall use of sunscreens and reduced incidences of sunburn and UVA exposure. However, existing formulations can have drawbacks, such as skin tightening, odor or limited durability on the skin; such drawbacks are attributed to film-forming polymers in used in sprays.
Polyamides and other synthetic polymers have been used as film-formers for personal care uses, including, for instance, sunscreen lotions. However, since the available polyamides have low compatibility with ethanol, they have not been used for anhydrous ethanol sprays. In addition, many polyamides used in personal care are gellant materials, and do not have desirable durability or skin feel, without additional formulation ingredients.
The film-forming polymer in an ethanol-based personal care application is critical. Often, there are few other components in the formulation. The film-farmer must bind active components (e.g., sunscreen actives) and secure them to the skin while providing good resistance to sweat or water. Moreover, consumers demand products that are tack-free, non-oily, non-tightening, and have good skin feel, and these properties all depend on the film-former.
Current commercial ethanol-based sunscreens in the U.S. typically include 1 to 5 wt. % of an acrylates/octylacrylamide copolymer, typically an acrylic resin from AkzoNobel known as Dermacryl® 79 (see, e.g., U.S. Pat. No. 6,322,776). Such sunscreen formulations can also include other film formers such as dimethicone polymers or other skin protectants (see, e.g., U.S. Pat. Appl. Nos. 2009/0035234 and 2009/0324506). Other acrylate film formers have been described (see, e.g., U.S. Pat. Nos. 4,731,242 and 6,395,269). Acrylates/octylacrylamide copolymer resin generally meets the needs for the film former, as it secures sunscreen actives and provides reasonably good water resistance, but it has limitations with respect to skin feel and related properties, as described above. In addition, Acrylates/octylacrylamide copolymer resin films may shrink slightly when applied from alcohol, giving a feeling of skin tightening. When an ethanol-based spray is applied, the ethanol quickly evaporates, and the resin rapidly forms a continuous film layer on the skin. Panels evaluating ethanol-based sunscreens (including those containing the acrylate-based film formers) continue to ask for products with lower tack, lower oiliness, and a softer, non-tightening skin feel.
Ultraviolet radiation can be damaging to skin. Immediate damage may be in the form of erythema. More long term is the concern of carcinomas or even melanoma. For these reasons, photoprotective agents, known as sunscreens, have been incorporated into cosmetic compositions.
Film-forming agents normally help to maintain a desirable sun protection factor (SPF) by securing sunscreen actives to the skin and imparting sweat and water resistance, thereby allowing the sunscreen actives to do their job under challenging conditions. Because sunscreen actives are expensive, any film former that can minimize the amount of sunscreen actives necessary to achieve a targeted SPF rating is desirable. Film-forming agents that not only maintain but actually enhance SPF in an ethanol-based personal care product while also providing desirable skin feel are needed.
U.S. Pat. Appl. Publ. No. 2010/0310481 teaches compositions comprising a hydrocarbon oil, a UV screening agent, a C1-C3 monoalcohol, and a lipophilic polyamide. The applicants teach that the kinds of lipophilic polyamides commonly used for sunscreen emulsions are not suitable for use in anhydrous, ethanol-based formulations. The exemplary formulations include 33 wt. % of capric/capyrlic triglyceride, 13 wt. % of a C12-C15 alkyl benzoate, and 6 wt. % of a particular polyamide resin; the description teaches that a wide variety of lipophilic polyamides are suitable. However, our own work indicates that many of the listed polyamides are incompatible with ethanol, particularly at low polyamide concentrations (e.g., 1-5 wt. %), and are therefore unsuitable for use in a continuous sunscreen spray.
A variety of polyamides and copolymers are well-known gellants for personal care, cosmetics, and air freshening (see, e.g., U.S. Pat. Nos. 6,268,466; 6,399,713; and 5,783,657). For additional examples, see U.S. Pat. Nos. 6,503,522; 6,960,339; and 7,989,002 and U.S. Pat. Appl. Publ. Nos. 2002/0127192 and 2006/0292095 (lipsticks or cosmetics); U.S. Pat. Nos. 5,500,209 and 7,744,857 (deodorants, antiperspirants); and U.S. Pat. Nos. 6,552,160 and 7,253,249 (candles and air fresheners). U.S. Pat. Appl. Publ. No. 2009/0324659 describes sunscreen composite particles useful for cosmetics that may comprise a polyoxyalkylene polyamide resin such as Polyamide-3. Ethanol-based sunscreens that contain Polyamide-3 (as Sylvasol™ 80 specialty polymer, product of Arizona Chemical) are also described.
U.S. Pat. Appl. Publ. No. 2010/0272657 teaches use of an amine additive to neutralize acid groups of a film-forming polymer, thereby improving the SPF rating. However, polyamides are not used as the film-forming polymer.
Emulsions useful as body lotions, sunscreens, and the like continue to be mainstays in the personal care arena. Formulators need emulsions that have good shelf life and maintain an acceptable SPF rating even after exposure to sweat or water immersion.
A need remains to identify improved compositions for use in body lotions, sunscreen lotions, continuous spray sunscreens, body splashes, and other personal care products. Of particular interest are ethanol-compatible, film-forming polymers that can give a clear solution with sunscreens, fragrances, cosmetics, medications, or other active components, and can be applied to the skin, hair, or scalp as a spray to leave a water-resistant film.
Preferably, the film-forming polymer would enhance the formulation SPF to minimize the amount of sunscreen actives needed. Many sunscreen agents are greasy or sticky when applied to the skin. Current polymers in sunscreen sprays cannot be used in amounts to overcome these properties and still provide a good film when sprayed onto skin. Consumers would like sunscreens in which the film-forming polymer can overcome greasy or sticky characteristics of sunscreen actives and still have good skin feel. Consumers also would like formulations that did not tighten the skin as they dry. In addition, formulators would prefer a film-forming polymer that would boost SPF so that less of the sunscreen active would be required to get an equivalent SPF.
A valuable ethanol-based composition would be homogeneous, sprayable using a valve-on-bag spray can or pump, and provide a continuous, even film at skin protection factors up to SPF 100. Ideally, the formulation would delight customers with low tack, low oiliness, and a soft, non-tightening skin feel when compared with commercially available ethanol-based sprays. Additionally, improved emulsions having good stability, acceptable SPF ratings, and good water resistance are always in demand.